Dental impression wafers, as disclosed in U.S. Pat. No. 3,604,116, having a sheet carrier of strong pliable material sandwiched between deformable impression material such as bite wax are known. The wafer permits a precise visual indication of premature engagement of the teeth and bite deflection. The wafer however does not permit measurement or monitoring of the bite force or force exerted on the wafer by the patient during occlusal analysis, or, more specifically, sliding bite force anaylsis, which analyses may suggest left/right muscular disbalance due possibly to premature contact or deflected contact between teeth of the maxilla and mandible. The force exerted during occlusal analyses can now be monitored, and permanent records of the force exerted on either side of the mouth are readily obtainable. These records may be used to later compare the patient's muscle activity before and after correction and adaptation.
Briefly, the invention comprises a stack of two superposed thin metallized films of polymer material having piezoelectric properties. The stack is coated on substantially all outer surfaces and edges with a conventional dental impression material, typically bite wax. The polymer film is preferably KYNAR.RTM. piezofilm, a polyvinylidene fluoride product of Pennwalt Corporation, Philadelphia, Pa., assignee of the present invention, although copolymers of vinylidene fluoride have been found to work satisfactorily.
The wax retains visible impressions of the relative positions and shapes of the tooth crowns, as well as bite deflection and premature teeth engagement indicia. The wax should deform plastically without affecting the spatial relationship of the teeth, and normally such condition obtains if the carrier sheet thickness is maintained below about 0,025 mm. The stacked piezoelectric film material, on the other hand, permits sliding bite force measurements to be precisely continuously monitored, which measurements may be permanently recorded by conventional means. If the total thickness of both piezoelectric films is greaer than about 0.025 mm, an artificial prematurity may result.